In his first-ever interview, the sole Australian survivor of the Waco siege has revealed to 60 Minutes what really took place during the 51-day stand-off, and why he believes crazed cult leader David Koresh will one day return to Earth as the son of God.

Sebastian Junger and Nick Quested, as two of the world's most acclaimed war documentary filmmakers, have witnessed the horrors of mankind.

Their films include Restrepo, the 2011 Oscar-nominated documentary depicting the year Junger and the late British photojournalist Tim Hetherington were embedded with a US Army platoon in Afghanistan's Korengal Valley, considered one of the most dangerous postings in the US military.

American Junger and UK-born Quested, in what could be their last war film, have turned their attention to the terror group Islamic State (ISIS) and the Syrian civil war with Hell on Earth: The Fall of Syria and the Rise of ISIS.

"We both felt it was possible to make a 90-minute survey of the Syrian civil war to explain how it started, why it got so bad and why ISIS came out of this situation," Junger said.

The duo said they hoped there could be peace in five or 10 years' time in Syria but it would take Russian involvement.

"I think you would have to bring the Russians in on that," Junger said.

"You would have to crush ISIS. Bring the Russians in and figure out a partition like they did with Bosnia which requires Russian co-operation."